Alliance/Encore L4-1721cc 105 CID (1985)
Fuel Pressure Regulator: Description and Operation
Renix Throttle Body Fuel Injection (TBFI), Late Type System
Fig. 2 Fuel pressure regulator
The fuel pressure regulator, Fig. 2, is an overflow type and is integral with the throttle body. The valve is a diaphragm operated relief valve in which one
side is exposed to air horn pressure and the other side is exposed to fuel pressure. Nominal pressure is established by a calibrated spring.
The pressure regulator has a spring chamber which is vented to the same pressure as the injector tip. The differential pressure between the injector nozzle
and the spring chamber is the same. Therefore, the volume of fuel injected is dependent only on the length of time the injector is energized. The pump
delivers more fuel than required by the engine and the excess is returned to the tank by the pressure regulator through the fuel return hose.
The fuel pressure regulator is not controlled by the ECU.
